In a wireless communication network, a mobile station operates in at least two modes. In an active mode, the mobile device is in active communications and is transmitting and receiving messages with a base station. In a dormant mode, the mobile device performs as few functions as possible, including limiting the number of messages being transmitted to the base station, in order that the mobile device conserves battery power. As such, the mobile station may wake-up at given periods of time to determine if a paging message is being sent to it from the base station serving the cell in which the mobile station is operating.
When a mobile device is in its dormant mode, the base stations and other network infrastructure equipment may not know the location of the mobile station because the mobile station is not sending any messages for the network with which the network can locate the mobile station. Accordingly, there are known a number of different models in which a mobile device is paged when it is dormant mode. One prior art approach is to page the mobile over the entire paging zone. This approach can be expensive in terms of paging costs, battery resources and other network resources because of the size of the paging zone and the energy needed to page over that area.
In another approach, the wireless communication network uses a hierarchical model, as shown in FIG. 1, to page the mobile stations. In this hierarchical model, the base station begins by paging the mobile station only in the last known zone at the first paging interval 102. As seen, the last known zone is represented by bar 104. If the mobile station does not respond, the base station then pages in neighboring areas, represented by bars 106, 108, at a second paging interval 110, 112. The number of areas and the size of the paging zones can be adjusted depending on resources and network performance factors. This approach, however, can add a large amount of delay in establishing communication when the target mobile station is not in the last known zone. The delay can be equal to an entire additional paging cycle or more than one such cycle.
Alternatively, the mobile station can be placed in a tighter mobility tracking mode. In this mode, the network uses location services, such as global positioning services, to determine the location of a mobile station. This approach also consumes battery resources as well as access channel capacity in performing the numerous updates needed to locate the mobile station.
In addition, the mobile station or access terminal can wake up very frequently, e.g. every 80 ms. This enables hierarchical paging to reduce the number of pages that need to be sent, but it can cause an issue for battery life. Specifically, it can drain the battery approximately 30 times faster where the mobiles paging interval normally is 2.4 seconds. Thus, it is not a viable to have a mobile wake up more frequently in order to make hierarchical paging practical. In view of the foregoing, there is a need to overcome the deficiencies of the prior art in paging a mobile station. In this way battery life can be conserved.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.